Quick-connect valved coupling devices for fluid systems commonly include a male coupling and a female coupling which are also herein referred to as a nipple and coupler, respectively. The male and female couplings are adapted to be interengaged with one another for interconnecting fluid conduits to which they are attached. Each coupling may be provided with a poppet valve which automatically closes the flow passage through the coupling when the male and female couplings are disconnected. When the male and female couplings are connected together, the poppet valves engage one another automatically to open the flow passages in the couplings for transfer of fluid through the mated couplings.
Some high pressure applications, such as compressed natural gas (CNG) vehicle refueling applications, require connection of a mating coupler at atmospheric pressure to a nipple even when the nipple is under pressure. A currently used prior art practice is to locate a check valve in line behind the nipple, thereby to isolate the poppet valve in the nipple from the pressure in the fluid conduit to which the nipple and check valve are attached. A problem arises when the check valve leaks as pressure can then become trapped behind the nipple's poppet valve. This trapped pressure may prevent connection of the mating coupler to the nipple. Another problem is that mechanical opening and/or closing of the nipple's poppet valve under high pressure exposes the valve seal therein to high forces and stresses which may cause the valve seal to chip, tear or crack and thereby reduce its life expectancy.